9.3 Lighting and Shading in 3D Compositing

Lighting and shading in 3D compositing are crucial for creating realistic scenes. From global illumination to HDRI lighting, these techniques simulate how light interacts with objects. They add depth, realism, and atmosphere to 3D elements, making them blend seamlessly with live-action footage.

Shading and textures bring 3D objects to life. Specular highlights, reflections, and subsurface scattering mimic real-world material properties. Normal maps add surface detail without increasing polygon count. These techniques are essential for creating believable 3D elements in composited scenes.

Lighting Techniques

Global Illumination and Ambient Occlusion

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• Global illumination simulates realistic lighting by calculating how light bounces and interacts with surfaces in a scene
  • Takes into account direct and indirect light sources
  • Produces more natural-looking shadows and reflections (soft shadows, color bleeding)
• Ambient occlusion adds realistic shading to crevices and corners where light is less likely to reach
  • Approximates global illumination by darkening areas that are close together or occluded
  • Enhances depth perception and realism in a scene (wrinkles in fabric, cracks in walls)
  • Can be calculated in real-time or pre-rendered for better performance

HDRI Lighting and Light Wrap

• HDRI (High Dynamic Range Imaging) lighting uses 360-degree panoramic images to light a scene
  • Captures a wide range of brightness levels from the environment
  • Provides realistic reflections and lighting without the need for manual light placement
  • Common in outdoor scenes or environments with complex lighting (city streets, forests)
• Light wrap is a technique that simulates the way light wraps around objects in the real world
  • Adds a subtle glow or halo effect around the edges of objects
  • Helps integrate 3D elements into a live-action plate by mimicking the light spill from the environment
  • Can be achieved through various methods (light maps, vertex colors, compositing tricks)

Light Linking

• Light linking allows artists to specify which lights affect which objects in a scene
  • Provides greater control over the lighting and shading of individual elements
  • Useful for isolating lighting effects or creating specific moods (spotlight on a character, rim light on a product)
  • Can improve rendering performance by reducing the number of lights that need to be calculated for each object

Shading and Textures

Specular Highlights and Reflections

• Specular highlights are the bright spots that appear on shiny or glossy surfaces when light hits them
  • Controlled by the specular color, intensity, and shininess of the material
  • Convey information about the material properties and lighting conditions (metallic vs. plastic, sharp vs. soft reflections)
• Reflection maps capture the environment surrounding an object and use it to create realistic reflections on its surface
  • Can be pre-rendered or generated in real-time using techniques like cube mapping or screen-space reflections
  • Add a sense of realism and depth to materials like metal, glass, or water

Subsurface Scattering and Normal Maps

• Subsurface scattering simulates the way light penetrates and scatters inside translucent materials
  • Produces a soft, diffused appearance in materials like skin, wax, or marble
  • Calculated by tracing the path of light as it enters, bounces around, and exits the material
  • Can be approximated using techniques like texture maps or pre-computed radiance transfer
• Normal maps are textures that store surface detail and roughness information in the form of RGB color values
  • Add fine details and bumpiness to a surface without increasing the polygon count
  • Enhance the appearance of materials like brick, stone, or leather by simulating surface irregularities
  • Can be created from high-resolution models or generated procedurally using algorithms like Perlin noise